1. Field of the Invention
This invention relates to a wafer polishing apparatus. More particularly, this invention relates to a polishing apparatus, for semiconductor wafers, using chemical mechanical polishing (CMP).
2. Description of the Related Art
Miniaturization of ICs (integrated circuits) has made progress in recent years, and IC patterns are being formed in multiple layers. A surface of the layer, on which such a pattern is formed, unavoidably has an unevenness to a certain extent. The prior art technology forms, as such, a pattern on the previous layer. The greater the number of layers and the smaller the widths of lines and the diameters of holes, the more difficult it becomes to form satisfactory patterns and the more likely it becomes for defects to occur. Therefore, it is a customary practice to planarize the surface of a layer having a pattern formed thereon and then to form the pattern of a next layer. A wafer polishing apparatus (CMP apparatus) using a CMP method has been employed for polishing a wafer during the formation of such an IC pattern.
In the wafer polishing apparatus according to the prior art described above, the steps of adsorbing a wafer one by one by a head from a cassette storing it, polishing and washing of the wafer, removing of the wafer from the head and accommodating of the wafer into the cassette, have been carried out batch-wise. Therefore, the conventional wafer polishing apparatus involves the problem of low through-put, hence low productivity.
In view of the problem described above, it is therefore an object of the present invention to provide a wafer polishing apparatus having improved through-put and high productivity.
A wafer polishing apparatus according to the present invention improves through-put by providing waiting units having wafer placement tables of an upper-lower two-stage structure for temporarily placing a wafer, capable of sliding individually, to a polishing unit.
A wafer polishing apparatus according to another embodiment of the invention uses an upper-stage wafer placement table of a waiting unit for a loading-only table and a lower-stage wafer placement table of the waiting unit for an unloading-only table.
In a wafer polishing apparatus according to still another embodiment of the present invention, when an upper-stage wafer placement table reaches a position at which a wafer is delivered to a polishing head, the wafer placement table is communicated with a feed water pipe so that the wafer can float up on the wafer placement table and the polishing head can easily hold the wafer.
In a wafer polishing apparatus according to still another embodiment of the invention, a washing unit comprising a ring-like brush and a water injection nozzle for washing a wafer holding surface of a polishing head is provided to a polishing unit. Therefore, the polishing head can be washed every time the wafer is polished, scratches on the wafer due to adhesion of dust can be prevented, and high precision planarization polishing can be conducted.
In a wafer polishing apparatus according to still another embodiment of the invention, a washing unit is disposed in a space below a position at which the wafer held by a wafer placement table of a waiting unit is delivered to a polishing head. Therefore, the installation space of the washing unit can be saved, and the polishing unit can be rendered compact.
In a wafer polishing apparatus according to still another embodiment of the invention, a ring-like brush and a wafer holding surface of a polishing head as a surface to be washed are arranged eccentrically relative to each other, so that relatively unmovable portions (unwashed portions) between the ring-like brush and the to-be-washed surface can be eliminated, and washing can be conducted sufficiently.
In a wafer polishing apparatus according to still another embodiment of the invention, a washing unit of a wafer holding surface of a polishing head and waiting units having upper-lower two-stage structure and capable of sliding individually are provided to a polishing unit. Therefore, through-put can be improved, and high precision planarization polishing can be conducted.
The present invention may be more fully understood from the description of a preferred embodiment of the invention set forth below together with the accompanying drawings.